These studies continue to explore the biochemistry of synovium and cartilage in experimental animal joints subjected to acute trauma. Minimal surgical trauma to rabbit knees, in the form of either sham surgery (arthrotomy only), or cartilage scarification has, to date, shown little biochemical or morphological change in the synovium or cartilage. In vitro degradative studies continue, attempting to measure proteoglycan matrix release from labelled cartilage incubated directly in contact with injured synovium. Preliminary results would indicate an inhibition of such release by synovium, although these reports are not complete. Continuing projects involve further experimental intra-articular trauma, (displaced fractures, inflammatory arthritis, etc.), for comparison with previously constructed models. These studies continue toward the goal of identifying a biochemically measureable endpoint in the progression of cartilage injury to traumatic arthritis, prior to which changes are reversible, and beyond which degenerative changes are inevitable.